We demonstrate a novel fiber endface photoacoustic (PA) generator using infrared (IR) 144 laser dye dispersed within an ultraviolet adhesive. The generator provides a wide acoustic bandwidth in the transducer frequency range of 2-7 MHz, high thermal conversion efficiency ($\gt90\%$), good PA signal controllability (well-controlled IR 144 concentration), and high feasibility (simple procedures). Through a series of experimental validations, we show that this fiber-based endface PA generator can be a useful tool for a broad range of biomedical applications such as calibrating the local absorption coefficient of biological tissue for quantitative PA tomography.We report on a watt-level highly efficient europium laser operating at the $^5\rm D_0 \to ^7\rm F_4$ transition. It is based on the stoichiometric $\rm KEu(\rm WO_4)_2$ crystal. Under pumping by a green laser at 532.1 nm, the $\rm KEu(\rm WO_4)_2$ laser generated a maximum peak output power of 1.11 W at $\sim703\;\rm nm$ with a slope efficiency of 43.2% and a linear polarization ($E\\;N_m$). A laser threshold as low as 64 mW was achieved. True continuous-wave operation was demonstrated. The polarized emission properties of monoclinic $\rm KEu(\rm WO_4)_2$ were determined.We present the experimental investigation of timing jitter and relative intensity noise of a Mamyshev ring oscillator operating in the fundamental mode-lock regime. We find that both timing jitter and intensity noise spectra are correlated to the output optical power with noise increase close to the loss of the mode-locking. In addition, we have investigated the dependence of the spectral filters wavelength separation on both timing jitter and intensity noise showing a severe degradation with filters overlapping.This paper analytically and numerically investigates misalignment and mode-mismatch-induced power coupling coefficients and losses as a function of Hermite-Gauss (HG) mode order. We show that higher-order HG modes are more susceptible to beam perturbations when, for example, coupling into optical cavities the misalignment and mode-mismatch-induced power coupling losses scale linearly and quadratically with respect to the mode indices, respectively. As a result, the mode-mismatch tolerance for the $\rm HG_3,3$ mode is reduced to a factor of 0.28 relative to the currently used $\rm HG_0,0$ mode. This is a potential hurdle to using higher-order modes to reduce thermal noise in future gravitational-wave detectors.Improving the imaging speed of multi-parametric photoacoustic microscopy (PAM) is essential to leveraging its impact in biomedicine. However, to avoid temporal overlap, the A-line rate is limited by the acoustic speed in biological tissues to a few megahertz. Moreover, to achieve high-speed PAM of the oxygen saturation of hemoglobin, the stimulated Raman scattering effect in optical fibers has been widely used to generate 558 nm from a commercial 532 nm laser for dual-wavelength excitation. However, the fiber length for effective wavelength conversion is typically short, corresponding to a small time delay that leads to a significant overlap of the A-lines acquired at the two wavelengths. Increasing the fiber length extends the time interval but limits the pulse energy at 558 nm. https://www.selleckchem.com/products/blu-945.html In this Letter, we report a conditional generative adversarial network-based approach that enables temporal unmixing of photoacoustic A-line signals with an interval as short as $\sim38\;\rm ns$, breaking the physical limit on the A-line rate. Moreover, this deep learning approach allows the use of multi-spectral laser pulses for PAM excitation, addressing the insufficient energy of monochromatic laser pulses. This technique lays the foundation for ultrahigh-speed multi-parametric PAM.Forward stimulated Raman scattering (SRS) induced by focused 400 nm pulses chirped to different pulse durations is observed in water and heavy water. The first Stokes Raman peak shift is shown to be tunable in the range of $3500 - 4200\;\rmcm^- 1$ in water and $2450 - 3250\;\rmcm^- 1$ in heavy water. It is demonstrated that the Stokes peak shift increases for shorter pulse durations and higher intensities.Nanophotonic modes within rectangular cross sections are typically considered to have transverse rectangular field profiles. In this work, we show that, despite the rectangular cross section of most integrated waveguides and microring resonators, there exists considerable hybridization of transverse rectangular modes and transverse circular modes. These hybridized modes can be advantageous in nonlinear wave mixing processes. We use third-harmonic generation as an example to confirm that such a hybridized mode is advantageous in combining reasonable mode overlap and waveguide coupling to a fundamental mode in a silicon nitride microring. Our work illuminates the potential of using transverse circular modes in nanophotonic applications.A multipass cell for nonlinear compression to few-cycle pulse duration is introduced composing dielectrically enhanced silver mirrors on silicon substrates. Spectral broadening with 388 W output average power and 776 ?J pulse energy is obtained at 82% cell transmission. A high output beam quality ($\rmM^2 \lt 1.2$) and a high spatio-spectral homogeneity (97.5%), as well as the compressibility of the output pulses to 6.9 fs duration, are demonstrated. A finite element analysis reveals scalability of this cell to 2 kW average output power.The local variations of group and phase propagation delays induced by bending and twisting a coupled core three-core fiber are experimentally characterized, for the first time, to the best of our knowledge, along the fiber length, with millimeter-scale spatial resolution. The measurements are performed by means of spectral correlation analysis on the fiber's Rayleigh backscattered signal, enabling for a distributed measurement of the perturbation effects along the fiber length. A mathematical model validating the experimental results is also reported.We present a novel, to the best of our knowledge, InGaAs/InAlAs single-photon avalanche diode (SPAD) with a triple-mesa structure. Compared with the traditional mesa structures, the horizontal distribution of the electric field decreases dramatically, while the peaks of the electric field at the mesa edges are well eliminated in the triple-mesa structure, leading to an excellent suppression of the surface leakage current and premature breakdown. Furthermore, the temperature coefficient of the breakdown voltage was measured to be as small as 37.4 mV/K within a range from 150 to 270 K. Eventually, one of the highest single-photon detection efficiencies of 35% among all the InGaAs/InAlAs SPADs with a decent dark count rate of $3.3 \times 10^7\;\rm Hz$ was achieved at 240 K. Combined with the inherent ease of integration of the mesa structure, this high-performance triple-mesa InGaAs/InAlAs SPAD provides an effective solution for the fabrication of SPAD arrays and the on-chip integration of quantum systems.